Cotter pins conventionally take the form of split pins which are inserted into a transverse bore in a shaft to prevent the shaft from moving longitudinally out of its bearings. The pin is inserted by hand or by a tool whereupon the two split ends are spread apart with the aid of the tool to prevent unintentional removal of the pin. When it is desired to remove the pin a tool must also be used to straighten the bent ends. These insertion and removal procedures, with the necessity for tools, are more often than not time consuming and tiresome, particularly when the pin is deployed in relatively inaccessible locations. Moreover, once deployed, a removed split pin may not be readily used again due to the deformities and weakening imparted during insertion and removal. Further, most split cotter pins do not fit solidly in the shaft hole and therefore create considerable slack between the pin and shaft.
A prior art attempt at overcoming the aforementioned disadvantages of the split cotter pin is found in U.S. Pat. No. 3,263,552 to Fischer. That patent discloses a bent resilient wire which includes a pin portion extending through the shaft bore and a ring portion which surrounds the shaft concentrically. This device leaves two of the split cotter pin problems unsolved. The first unsolved problem resides in the fact that the portion of the device which is inserted in the transverse shaft bore does not solidly fit therein resulting in significant slack between the pin and shaft. The other unsolved problem resides in the fact that, although no tool is required to deploy the resilient device, the deployment requires that the pin and ring portions must be forced apart to effect deployment and removal, the required force being such that two hands are generally required. Deployment and removal, therefore, are not easy to accomplish in locations having difficult access. Moreover, forcing the two portions apart often results in permanent deformation of the device, rendering it useless for its intended purpose.
Prior art retainer rings are generally incomplete annular members which surround a reduced-diameter portion of a shaft to be retained. Such devices are resiliently spread open for purposes of deployment and removal. Often, particularly in locations of limited access, spreading of the retainer ring to effect deployment and/or removal is difficult at best.
Prior art shaft couplings tend to be either difficult to deploy or expensive. Many such couplings are unable to tolerate axial, radial and/or angular misalignment of the coupled shafts. Some shaft couplings must be permanently mounted on the shafts and are unable to be removed without being destroyed.